Acetylcholine (ACh) acts as a local hormone at surface cholinergic receptors and enhances sperm motility. Activation of surface cholinergic receptors is transducted to elements generating intracellular signals (e.g., Ca++) which are required for motility. Two transduction mechanisms are well delineated in membranes: (a) a phosphatidylinositol (PI)-phophatidic acid (PA) system, and (b) a phospholipid N-methyltransferase (PMT) system. These systems are present in spermatozoa and influence sperm motility. Opioid peptide-like and Substance P-like peptides which modulate actions of ACh occur in spermatozoa and seminal plasma. Therefore, the following specific aims are selected to establish the relationships between the spermic cholinergic system, membrane transduction mechanisms, sperm motility, and fertility: 1. Characterization of acetyl group transferring enzymes in sperm (choline and carnitine acetyltransferases, ChA, CaA). Effects of the inhibition of ChA and CaA on sperm motility. 2. Localization and distribution of ChA and CaA using fluorescent and radiolabeled inhibitors. 3. Alternate sources of choline for ACh synthesis in spermatozoa. 4. Activation of PI-PA and PMT systems in spermatozoa and the effects of their inhibition on sperm motility. 5. Enzyme activities of cholinergic, PMT and PI-PA systems in capacitated sperm (man, bull, and guinea pig), split ejaculates (man), and sperm fractions (bull: heads, midpieces, and tails). 6. Separation and characterization of opioid peptides (methionine enkephalin, leucine enkephalin, Beta-endorphin) and Substance P from spermatozoa, seminal plasma, and accessory sex glands (seminal vesicles, prostate gland). 7. Influence of opioid peptides and Substance P on sperm motility and Ca++ transport in spermatozoa. Effect of enkephalinase inhibitors on sperm motility. 8. Effects of environmental sterility agents (trimethylphosphate, 1:2-dibromochloropropane, Alpha-chlorohydrin, cyproterone acetate) on enzymes of the cholinergic (acetyle-CoA synthetase and ChA), PMT (enzymes I and II), and PI-PA (phospholipases C and D) systems and their antifertility indices in vivo (mice and rats). This investigation will be useful to (1) explain the role of ACh, PMT and PI-PA systems in the regulation of sperm motility; (2) understand infertility in men who ejaculate immotile sperm; (3) explain transient infertility among male smokers; and (4) develop antifertility agents.